AI coding agents love to run tests in parallel processes.
That’s great until multiple processes try to use the same local test database at once. A small file lock can serialize access and stop those runs from stepping on each other.
PHP
Laravel Deadlocks: Queue Jobs That Already Ran End Up in failed_jobs
Below MySQL 8.0.1, or on a server Laravel misreads, workers reserve jobs with a plain FOR UPDATE and can deadlock on the DELETE. One tinker line shows which lock yours use. Read more